The invention relates to a hard-shell capsule of a type used to deliver dosages of pharmaceuticals, medicines, vitamins, dietary supplements, etc. . . . to an individual. The invention is suitable for any dosage form but is most particularly adapted to liquid dosages.
In general, hard-shell capsules are made of two separately moulded parts, namely a body and a cap. In the manufacturing process, the cap is placed on the body in a pre-closed position providing a sufficient retention force for the transfer of pre-assembled capsules to the filling machine with no risk of separation.
In the filling machine, successive capsules are automatically processed according to the following steps:                the cap is removed from the body;        the body is filled with a dosage;        the cap is positioned again on the body and locked in a fully closed final position.        
In the fully closed final position, the force to disengage the cap from the body is much higher than in the pre-closed position.
During the final joining of the capsules after filling, there is a risk that the cap is not properly fixed on the body, due to the air pressure increase inside the capsule upon closing. It is thus desirable that the air excess is allowed to escape from the inner volume of the capsule when the final assembling is processed. Therefore, it has been proposed to provide capsules with means allowing air escape.
The invention relates to such hard-shell capsules comprising:                a hollow tubular body elongated in an axial direction, having a closed end and an open end,        a hollow cap slidably and telescopically engageable on the body in the axial direction from a disengaged position into a fully closed final position,        the body and the cap defining an inner volume therebetween and being provided with complementary snap-fit means for locking the cap on the body in the fully closed final position,        the complementary snap-fit means comprising a locking ring formed by a channel on an axial section of the body and a complementary ridge member formed on the inner surface of the cap so as to protrude inwardly,        at least one air-vent formed as an axial recess on the outer surface of the body and suitable for ensuring fluid communication between the inner volume and the atmosphere over a range of engagement positions of the cap on the body.        
Such a capsule is known in the prior art, for example from U.S. 2007-0184077 A1, wherein the air-vents are formed by oval dimples extending across the locking ring.
However, due to the structure of the dimples, the air escape is only allowed on a small range of engagement positions between the pre-closed position and the fully closed final position. On the remaining travel of the cap until the full engagement, the air pressure builds up in the capsule. This may cause some deformations of the capsule and the fill product, especially in case it is a liquid dosage, may leak out of the capsule before a tight sealing is made. Such leakage may occur during the transfer between the filling machine and a sealing machine, especially if the capsules are not vertically transferred.
It is an object of the invention to solve the aforementioned problem and propose a capsule design suitable to minimize the risks of leakage of the capsule after filling.
It is a further object to propose a capsule design which is adapted to the large scale manufacturing processes.